/*
  将下面异步代码使用 Promise 的方法改进
  尽量用看上去像同步代码的方式
  setTimeout(function () {
    var a = 'hello'
    setTimeout(function () {
      var b = 'lagou'
      setTimeout(function () {
        var c = 'I ♥ U'
        console.log(a + b +c)
      }, 10)
    }, 10)
  }, 10)
*/
var a = 'hello';
var b = 'lagou';
var c = 'I ♥ U';
function proSet(value) {
  return new Promise((resolve, reject) => {
    setTimeout(function () {
      var a = value
      resolve(a);
    }, 10)
  })
}

Promise.all([proSet(a), proSet(b), proSet(c)]).then((res) => {
  var sum = '';
  res.forEach(item => {
    sum += item;
  })
  console.log(sum);
})

